Next, some real answers about the top resolution every new year. To lose weight. Most people who try will fail. But there are a small percentage who lose the weight and keep it off. And abc's linsey davis takes us inside these secrets of the superdieters. Drop a jean size -- Reporter: 'Tis the season of dieting. So many of us motivated to shed the pounds. I lost 50 pounds in about 6 months. Reporter: Take marshall brain. We followed his journey on the dukan diet. But when we returned, the pounds were starting to pack back on. 233. One pound away. One. Reporter: Kalia moss went on the best-selling rehab diet in 2012. So hungry. Reporter: And similarly, in the long run, she wasn't able to keep the weight off. I was able to keep it off for a little bit. And I gained it back and a little bit more. Reporter: Turns out, they're among the 85% of dieters who fail. Recent studies say it's a matter Your body starts to create hormones that make you feel hungrier. The brain responds more to food cues, telling you to eat those foods. Reporter: But there is an elite group. People who have beaten the odds. They're called superdieters. They've not only lost weight. They've kept it off for years. More than 10,000 of them are being tracked in aatabase by the national weight control registry. We've been able to study these individuals carefully and find out what strategies have been related to their success. Reporter: The data suggests there are golden rules to these superdieters. Rule number one, don't cheat. They never give themselves a break. Not even on holidays or weekends. And rule number two, eat breakfast. Get this. The registry shows that's one of the most common traits of those who succeed in keeping those pounds off once and for all. And some good news? There is a point where it does get easier. The registry suggests if you keep off the weight for two years, you're probably going to have a much better chance of keeping it off long-term. Reporter: The two rules that we mentioned, just the tip of the iceberg. Tomorrow, we meet some of these superdieters and learn their secrets of the scale. For example, diane, how often do you think they weigh themselves? We're going to have that answer for you and a lot more tomorrow night. I want to know. Thank you, linsey. You'll be here tomorrow night. Yeah.

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